1. Field of the Invention
The present invention relates to technologies for detecting nitrogen oxides (hereinafter being abbreviated to as “NOx”) that exhaust gases include. More specifically, the present invention relates to a method of correcting NOx concentrations that NOx sensor detects actually. Moreover, the present invention relates to an NOx-sensing device that comprises an NOx sensor, and a corrector for correcting NOx concentrations that the NOx sensor detects actually.
2. Description of the Related Art
An NOx sensor is a device for detecting NOx that exhaust gases include. For example, as Japanese Unexamined Patent Publication (KOKAI) Gazette No. 11-72,477 and Japanese Unexamined Patent Publication (KOKAI) Gazette No. 11-23,526 disclose, an NOx sensor has been usually disposed heretofore on an exhaust-gas flow passage's downstream side and/or upstream side with respect to an exhaust-gas converting catalyst that is put in place in the exhaust system of vehicle. Thus, the NOx sensor detects a concentration of NOx that exhaust gases include when the exhaust gases arrive at its vicinity.
Here, note however that the exhaust gases' NOx concentrations that the conventional NOx sensor detects differ slightly from the real or exact NOx concentrations in the exhaust gases. To be concrete, the exhaust gases' NOx concentrations that the conventional NOx sensor detects have been slightly lower than the real or exact NOx concentrations in the exhaust gases.
Moreover, the conventional NOx sensor, which is put in place on the exhaust-gas converting catalyst's upstream side and/or the downstream side, has been used for controlling the conversion actions of the catalyst and detecting the degradation. Accordingly, it is required for the NOx sensor to sense the NOx concentrations highly accurately. Consequently, it has been desired to devise a technology for making the NOx concentrations that the NOx sensor detects actually (hereinafter being referred to as “detected NOx concentrations or values”) closer to the real or exact NOx concentrations (hereinafter being referred to as “true NOx concentrations or values”), or for approximating the true NOx concentrations or values by using the detected NOx concentrations or values.